1. Field
The present disclosure relates to varifocal lenses.
2. Description of the Related Art
A lens is an instrument for concentrating or distributing light according to properties whereby light is refracted at a boundary surface between different media with different refractive indexes and is a basic component of various imaging devices such as cameras.
A focal length of a lens is determined according to a curvature of a lens surface and a material of a lens. Recently, demand for a lens system having a varifocal function for obtaining better images has increased. A varifocal function is used for an autofocusing operation or a zooming operation and is performed by mechanically moving some lenses constituting a lens system by using a motor or the like or by changing a curvature of a lens surface by using a liquid lens.
Recently, there has been increased interest in techniques for using a liquid crystal as an optical lens by electrically controlling the operation thereof. Liquid crystal molecules are aligned along the direction of an electric field. Since the refractive index in a major axis direction is generally different from the refractive index in a minor axis direction in the case of liquid crystal molecules, the liquid crystal molecules have various refractive indexes according to their alignment states. In particular, if a boundary surface, where the refractive index changes due to the alignment of liquid crystal molecules, is curved, the liquid crystal molecules refract light transmitted thereto, thereby acting as an optical lens.